GB1059307A - Improvements in electrostatic loudspeakers - Google Patents

Abstract

1,059,307. Electrostatic loud-speakers. A. SHACKMAN. April 30, 1965 [Feb. 12, 1965], No. 6155/65. Heading H4J. An electrostatic loudspeaker assembly comprises two outer rigid perforated zinc plates 1, 2 and an inner rigid perforated zinc plate 3. Plates 1 and 2 are parallel. but may be of overall non- plane shape, e.g. part-cylindrical. Intermediate flexible diaphragms 4, 5 of non-conductive plastics film are each metallized on that surface 4a, 5a which faces towards the inner plate 3. Their opposite surfaces, facing plates 1. 2, are non-conductive. Lengths of cotton 6a are secured along and in contact with both faces of the inner plate 3 at parallel positions. Similarly, lengths of cotton 6b are secured along and in contact with the non-conductive outer surface of each diaphragm 4, 5. The lengths of cotton may be portions of continuous filaments. The assembly is in the form of a lightly compressed sandwich without any spacing other than that dictated by the thickness of the cottons 6a, 6b. The surfaces 4a, 5a are in touching and electrical contact with the inner plate 3 except where they are held away by cotton 6a. The assembly is connected as shown to a transformer T, the primary winding P of which is connected to an audio-frequency source. The centre tap of the secondary winding S is connected to the negative pole of a D.C. polarizing voltage. The positive pole is connected through a 10 megohm resistor R to the inner plate 3.